Germany has opened an investigation into Facebook’s use of user data, which may be in breach of the country’s data protection laws, reports Reuters. The country’s watchdog, the Federal Cartel Office, is concerned that Facebook isn’t sufficiently informing users what data it collects about them and how the company uses their data, particularly in relation to advertising sales.

“For advertising-financed internet services such as Facebook, user data are hugely important,” Federal Cartel Office president Andreas Mundt said in a statement. “For this reason it is essential to also examine under the aspect of abuse of market power whether the consumers are sufficiently informed about the type and extent of data collected.”

Germany has some of the strongest data protection laws and regulations in Europe, so it’s no surprise the country is concerned about the way the world’s largest social network—with over 1.6 billion active monthly users—uses German citizens’ data.

As the Wall Street Journal notes the concern by the Federal Cartel Office is that Facebook could use its “possible market-dominant position” to force users to consent to the collection of “vast amounts of personal data from various sources,” which Facebook could then use to compile data sets that give them an unfair edge in the market, shutting out newer, fledgling firms.

Perhaps in anticipation of the Federal Cartel Office’s announcement of the investigation, Facebook CEO Mark Zuckerberg visited Berlin last week on a “charm offensive,” Reuters reports.

For Facebook’s part, a company spokesperson on Wednesday said, ”We are confident that we comply with the law and we look forward to working with the Federal Cartel Office to answer their questions.”MG